This invention relates to spurted polyolefin pulp. More particularly, the invention relates to spurted polyolefin pulp having precipitated thereon a natural rubber or a synthetic elastomer. The pulp is readily dispersible in organic media and is particularly useful as an additive to cutback asphalt compositions.
As is well known, cutback asphalt compositions have long been used, primarily in the construction industry, as coatings and cements. Typically, cutback asphalt compositions have a viscosity less than about 2,000 cps. In many instances, it has been desirable to include fibers in the compositions to thicken them while at the same time improving their rheology so as to permit ready spraying, brushing and trowelling. Asbestos has been particularly suitable as the fiber component of such asphalt compositions.
However, due to the health hazards associated with the use of asbestos, considerable effort has recently been directed in the art to the development of asbestos-free formulations having the desirable properties of the asbestos-based compositions. Considerable work has been done, for example, with synthetic fibers, including polyolefin fibers. Polyolefin fibers were found to be effective from the standpoint of thickening the cutback asphalt compositions, but the fibers exhibited a tendency to clump together and float on the surface of the compositions. Obviously, the polyolefin fibers did not remain well dispersed in the organic medium presented by the cutback asphalt compositions and as a consequence, the rheological properties of the compositions were very poor.
Now, in accordance with this invention, a cutback asphalt composition containing well dispersed polyolefin pulp has been found, said composition comprising asphalt, a hydrocarbon solvent and spurted polyolefin pulp having precipitated thereon a natural rubber or a synthetic elastomer. The pulp is readily dispersible in the cutback asphalt, remains well dispersed therein for several days and is easily redispersed using mild stirring if separation occurs after prolonged storage. Furthermore, the composition has the desired rheological properties and, upon application, is resistant to cracking and to slumping.
The indicated pulp is prepared by adding water dispersible spurted polyolefin pulp in low concentration to water; agitating the resulting mixture to form an aqueous dispersion of the pulp; adding to the dispersion, with continued agitation, an anionic latex of a natural rubber or a synthetic elastomer; precipitating said natural rubber or synthetic elastomer onto the polyolefin pulp by adding to the agitated aqueous dispersion containing said pulp and said anionic latex an agent capable of precipitating an anionic latex, preferably a water-soluble calcium, barium, magnesium or aluminum salt or calcium or barium hydroxide and then isolating the treated pulp so formed from the aqueous dispersion.